Hydrogen attack in a welded reactor

Abstract
Reactors for hydrocracking and hydrotreating are exposed to high hydrogen pressures at elevated temperature. The critical failure mechanism in these vessels is hydrogen attack, i.e. chemically-driven damage accumulation leading to intergranular failure. These rectors are typically manufactured by circumferential welding of forged belts made of 2.25Cr-1Mo steel, and the associated microstructural changes make these weldments especially suspectible to hydrogen attack. This paper summarizes a recently developed model that links the chemistry of hydrogen attack with the mechanical behavior through a damage model. This model is then incorporated into a finite element model and used to calculate the deformation and damage evolution, stress distribution and failure time of a welded reactor under internal hydrogen pressure.